Physiologic insults triggering the onset of systemic inflammatory conditions including sepsis, Adult Respiratory Distress Syndrome (ARDS), Systemic Inflammatory Response Syndrome (SIRS) and Multiple Organ Dysfunction Syndrome (MODS) have been identified to include infection and its systemic effects, shock, trauma, inhalation injury, pancreatitis, hypertransfusion, drug overdose, and near-drowning among others. The host response manifested in each of these insults includes increased capillary permeability, organ failure, and death. The mechanism of the response involves diffuse pathologic activation of inflammatory mediators including, but not limited to, endotoxin, leukotrienes B.sub.4, C.sub.4, D.sub.4 and E.sub.4, prostacyclin and thromboxane A.sub.2, activated granulocytes and complement components C3a and C5a, tumor necrosis factor, interleukin-1, interleukin-6, interleukin-8, and other cytokines, neutrophil elastase, platelet activating factor, nitric oxide, and oxide radicals.
Bone, R. C. Annals of Internal Medicine 115:457-469, 1991, reviews the pathogenesis of sepsis and provides a summary of what is known about mediators involved in this pathogenesis along with a hypothesis for understanding how these mediators produce the endothelial dysfunction believed to be one of the key derangements underlying sepsis. Bone (1991) discloses that sepsis and related disorders result in part from endothelial injury caused by repetitive, localized foci of inflammation which, in turn, produce an increase in capillary permeability. Bone suggests that this endothelial dysfunction is the result of the activities of a series of mediators responsible for the pathogenesis. It is proposed that the release of endotoxin or a comparable substance such as enterotoxin, toxic shock syndrome toxin-1, gram-positive or yeast cell-wall products, and viral or fungal antigens, is the initiating event in the sepsis cascade. Once in the circulation, the substance prompts the release of TNF-.alpha., interleukins, and platelet activating factor. Arachidonic acid is then metabolized to produce leukotrienes, thromboxane A.sub.2 and prostaglandins. Almost all of these agents have direct effects on the vascular endothelium. Other suggested agents which may participate in this sepsis cascade include adhesion molecules, kinins, thrombin, myocardial depressant substance, .beta.-endorphin, and heat shock proteins. Bone (1991) presents a pyramid-shaped model of sepsis based upon the theory that the mediators of sepsis can be shown to produce an expanding sequence of events according to the intensity or dose of the original insult. Starting from the top, this pyramid includes (1) infection; (2) release of endotoxin and other bacterial products; (3) release of mediators of inflammation (i.e., cytokines, eicosanoids); (4) sepsis--with or without multi organ failure; (5) sepsis syndrome--with or without multi organ failure; (6) septic shock--with or without multi organ failure; and (7) recovery or death. Bone (1991) suggests that this model may have important implications in the diagnosis and therapy of sepsis.
As a result of identifying causative factors of systemic inflammatory conditions such as sepsis and recent advances in the fields of monoclonal antibodies and recombinant human protein technology, several novel adjuvant treatments have been developed for patients with systemic inflammatory conditions such as sepsis, ARDS, SIRS and MODS. Experimental results and preliminary clinical data suggest that antibodies against gram-negative endotoxin and tumor necrosis factor, human recombinant protein antagonists of interleukin-1 and other cytokines, and inhibitors of platelet activating factor may be beneficial in sepsis, ARDS, MODS and other manifestations of SIRS. Other mediator modifying drugs, such as the cyclo-oxygenase inhibitor ibuprofen, and ketoconazole, a potent antagonist of thromboxane synthetase and 5-lipoxygenase may also be effective in the treatment of ARDS.
Bone, R. C. Clin. Micro. Rev. 6(1):57-68 (1993) provides a review of the epidemiology, diagnosis and current management of gram-negative sepsis and examines the therapeutic potentials of new treatments under development. A variety of physiological changes are disclosed which are associated with the development of sepsis including fever, hypothermia, cardiac manifestations, respiratory signs, renal manifestations and changes in mental status. In addition, important aspects of the effective management of sepsis and a review of current management strategies as well as recent advances including immunotherapy are disclosed.
The promise of these new drugs in the treatment of ARDS, sepsis, MODS and SIRS, however, has not been realized in confirmatory trials following pre-clinical and Phase II testing. One of the primary reasons for these therapeutic failures is the inability of investigators to identify specifically patients most likely to benefit from these treatments at an early stage in the host response, before the pathologic mediator activation that causes the systemic inflammatory response is manifested overtly. Accurate subclinical diagnosis and prediction of organ failure, septic shock and gram-negative infection are even less feasible. Consequently, patients are enrolled in prospective investigations of new treatments for ARDS, sepsis, MODS and SIRS using entry criteria that uniformly reflect late, clinically obvious sequelae of the underlying pathophysiologic processes. Studies of potentially beneficial drugs then fail because patients are enrolled after irreversible tissue damage has occurred, or because so many "at risk" patients must be entered to capture the target population that a drug effect can not be demonstrated, or because the spectra of disease entities and of clinical acuity in the study groups are too variable.
The optimal approach to Winding new treatments for ARDS, SIRS, MODS, sepsis and related conditions would be to test new therapeutics in specifically identified patients with high power, accurately predicted risk of developing ARDS, SIRS, MODS, sepsis or a related condition at a time when the acute pathophysiology is still subclinical. Although there are several physiologic scoring systems available which measure the severity of illness, the degree of sepsis, the severity of trauma, or the intensity of organ system dysfunction and are used by physicians to identify certain patient populations, these systems are all based upon obvious, late clinical manifestations of the underlying inflammatory phenomena. The predictive power, accuracy, and specificity of these systems, therefore, are limited.
The Injury Severity Score (ISS) was devised in 1974 as an adaptation of the Abbreviated Injury Scale (AIS). The ISS is a measure of the severity of anatomic injury in victims of blunt trauma and has been found to correlate well with mortality. The score is obtained by summing the squares of the three highest values obtained in five body regions, with 0 points for no injury and 5 points for a critical lesion. The ISS is the most widely used system for grading the severity of an injury; however, it has been criticized as there is a systematic under prediction of death and there is no adjustment for age as a risk factor. The hospital Trauma Index (HTI) is an adaptation of the ISS which contains both anatomic and physiologic elements in six body regions. A good correlation between ISS, HTI and AIS has been shown.
The Glasgow Coma Scale (SCS) was also introduced in 1974 as a simple, reliable and generally applicable method for assessing and recording altered levels of consciousness. Eye opening, best motor response and best verbal response are monitored and scored independently on a scale ranging from 3 (worst) to 15 (best). The GCS has shown good correlation with functional outcome of survivors and therefore has been incorporated into several other scoring systems.
The Trauma Score (TS) was developed in 1980 for rapid assessment and field triage of injured patients. The TS measures physiologic changes caused by injury. It consists of respiratory and hemodynamic information, combined with the GCS. The TS has been shown to have a high predictability of survival and death.
Physiologic (TS) and anatomic (ISS) characteristics are combined in the TRISS scoring method used to quantify probability of survival following an injury. The method was developed for evaluating trauma care but can be applied to individual patients to estimate the probability of survival.
The Sepsis Severity Score (SSS) was developed in 1983 for grading the severity of surgical sepsis. The system consists of a 6-point scale in seven organ systems including lung, kidney, coagulation, cardiovascular, liver, GI tract and neurologic. The final score is calculated by adding the squares of the highest three values of the three organs with the most severe dysfunction. Studies have shown significantly different scores in survivors versus nonsurvivors and the score correlated well with the length of hospital stay in the survivor group.
The Polytrauma Score (PTS.), developed in 1985, is an anatomic injury severity score including an age classification. The score is thought to be more practicable than the ISS while having good correlation with the ISS.
The Multiple Organ Failure Score (MOF score), developed in 1985, grades the function or dysfunction of the seven main organ systems including the pulmonary, cardiovascular, hepatic, renal, central nervous, hematologic, and gastrointestinal systems. This score has been shown to correlate well with mortality outcome.
Also in 1985, APACHE II, a revised version of APACHE (Acute Physiologic And Chronic Health Evaluation) was presented. APACHE II is a disease classification system developed to stratify acutely ill patients admitted to the Intensive Care Unit. Increasing scores have been shown to correlate well with hospital death. The score consists of an acute physiology score (APS), and age score, and a chronic health score. The APS is determined from the most deranged physiologic values during the initial 24 hours after ICU admission. The APACHE system, however, has not consistently predicted mortality risk for trauma patients. APACHE III is the latest revision of APACHE but like its predecessors, the system relies only upon clinically evident data and, therefore, is useful only for predicting mortality risk in selected groups of critically ill patients.
In a study performed by Roumen, R. M. et al., The Journal of Trauma 35(3):349-355, 1993, the relative value of several of these scoring systems in conjunction with measurement of plasma lactate concentration was examined in relation to the development of ARDS, MODS, or both in patients with severe multiple trauma. It was concluded that scoring systems directly grading the severity of groups of trauma patients have predictive value for late and remote complications such as ARDS and MODS, where as scoring systems that grade the physiologic response to trauma, while related to mortality, have no predictive value.
The scoring systems such as APACHE, TRISS, the Sepsis Score and the Multiple Organ Failure Score rely upon overt clinical signs of illnesses and laboratory parameters obtained after the appearance of clinical signs and, thus, are only useful in predicting mortality in a patient.
In a study performed on trauma patients at Denver General Hospital in Colo. Sauaia, A. et al., Arch Surg. 129:39-45, 1994, found that early independent predictors of postinjury multiple organ failure include age greater than 55 years, an Injury Severity Score greater than or equal to 25, and receipt of greater than 6 units of red blood cells in a 12 hour period. Subgroup analysis indicated that base deficit and lactate levels could add substantial predictive value.
Clinical application of any of these prior art scoring systems has been limited to an assessment of grouped percentage risk of mortality. None of the systems are applicable to individual patients. Furthermore, being limited only to predicting risks of hospital death, and possibly consumption of health care resources, the currently variable prognosticated systems can only categorize patients with similar physiology into like mortality risk groups; the systems do not predict important pathophysiologic events in individual patients that could facilitate timely therapeutic intervention and improve survival.
In order for pathophysiologic prognostication to become clinically beneficial to individual patients, a system must predict subclinically the physiologic insults and sequelae of systemic inflammation that lead to mortality in advance so that data-based interventions can be administered in a timely fashion and survival can be optimized. A key to achieving this new level of critical care prediction is to recognize temporal pathophysiology links between baseline clinical and subclinical data and subsequent events in the clinical course of individual patients.
In the present invention, a method for identifying systemic inflammatory conditions such as ARDS, SIRS, sepsis and MODS at a subclinical stage is provided which is based upon the simultaneous measurement of the physiological clinical response to pro-inflammatory insults and the subclinical activation of biochemical and cellular inflammatory mediators. This Systemic Mediator Associated Response Test (SMART) is useful in subclinically identifying patients at risk of developing ARDS, bacteremia, sepsis, SIRS, organ failure, MODS and other acute conditions before overt clinical signs of these tissue level phenomena become apparent. A SMART patient profile can be generated and compared to established baseline values or to a patient's normal values to assess a patient's risk of developing a systemic inflammatory condition.